Golarge,
My apologies for not responding sooner. I apparently hadn’t looked at this particular thread. I momentarily got hung up on the idea of applying heat while pumpung. Then after a period of time, mine varies between five and ten minutes, jelqueing for perhaps 100 jelques. Awsome feel. Anyway , to your question; the sweatshirt underwrap is simply a strip long enough to overlap each turn a small amount, perhaps 3/8 inch and wrap the whole length of what ever your upper wrap is, I use theraband(grey). I’m absolutely amazed at the difference in comfort. I hadn’t used this before, even though it is Bigger’s recommended underwrap, ‘cause I didn’t have an old ,worn out sweatshirt. The difference in comfort, for me would make it worth some considerable effort to find some of this material. Try it, you’ll love it.
Surfer1